Sandy Alderson is facing a more serious battle this winter than trying to improve the Mets.

The 68-year-old general manager has been diagnosed with a treatable form of cancer and will begin 8-12 weeks of chemotherapy, precluding him from attending the upcoming Winter Meetings in Nashville, Tenn., according to team COO Jeff Wilpon.

Alderson underwent an unspecified medical procedure three weeks ago that forced him to miss the General Managers’ meetings. During that procedure at Memorial Sloan Kettering, doctors confirmed Alderson has cancer.

“The doctors believe and have told Sandy that the cancer is very treatable and are optimistic about a full recovery,” Wilpon said.

Alderson will continue with his GM duties, but will rely heavily on assistant GM John Ricco, special assistant J.P. Ricciardi and vice president of development and amateur scouting Paul DePodesta during his treatments.

“There will be days [Alderson] may not be in the office,” Wilpon said. “In the meantime, Sandy’s team and I will be coordinating closely with him and keeping him up to date on all baseball matters.

“We wish him and his family the very best and look forward to this getting behind him.”

Concerns about Alderson’s health arose last month, when he fainted during a press conference at Citi Field to announce manager Terry Collins’ new two-year contract. Alderson was unresponsive for about 30 seconds before arising and apologizing to reporters. The Mets said Alderson hadn’t eaten breakfast that day and collapsed in part because he was overheated from the TV camera lights.

Alderson is helped to his feet after fainting at a Citi Field press conference in November.AP

But Alderson skipped the GM meetings in Boca Raton, Fla., which began days later, to undergo the surgery. The Mets said he had delayed the procedure because of the team’s postseason run, which ended with a loss to the Royals in Game 5 of the World Series.

Ricco, Ricciardi and DePodesta were active in trade discussions at the GM meetings in addition to initiating contact with agents.

“The nature of our business is we’re all moving around a lot, all the time,” Ricco said. “So it’s not like your typical [job] where everybody shows up at 9:00 in the morning and meets and then goes through the day. So [Alderson’s absence] is not going to be that big of an adjustment. We’ll have plenty of access to Sandy, we talk to him all the time. He’s a phone call away.”

Alderson, who recently was named Executive of the Year by Baseball America, agreed to a three-year contract extension last offseason that keeps him signed through the 2017 season. The Mets finished below .500 in each of Alderson’s first four seasons before ending a nine-year postseason drought in 2015.

“Sandy came in here and put a plan in place and stayed with it,” manager Terry Collins said earlier this week. “He never let the outside influences, be it fans or media, change what the philosophy was going to be. He stuck with it. He stuck with it offensively the kind of players he brought in here and changed the organization and it finally paid off for him.”